Sheetless Backlight Module, A Light Guide Plate for the Sheetless Backlight and Manufacturing Method Thereof

ABSTRACT

A sheetless backlight module and a light guide plate thereof are provided. The light guide plate includes a body and a plurality of light scattering units. The body has a bottom and a plurality of microstructures formed on the bottom and recessed in the body from the bottom. The pluralities of light scattering units are disposed in a plurality of spaces formed due to the plurality of microstructures recessed in the body. A manufacturing method of the light guide plate mentioned above includes forming the plurality of microstructures on the bottom of the body; preparing a fluid solution containing at least a diffusive reflective material; distributing the fluid solution on the bottom; driving the fluid solution to flow into the microstructures; removing the part of the fluid solution outside the microstructures; and solidifying the fluid solution to form the plurality of light scattering units.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a sheetless backlight moduleand a design of a light guide plate for the sheetless backlight module.Particularly, the present invention relates to a sheetless backlightmodule having a wider range of light-exiting angle and a light guideplate thereof.

2. Description of the Prior Art

Liquid Crystal Display (LCD) devices are extensively used in a varietyof electrical devices such as computers, televisions, and mobile phones,wherein a light guide plate is used in a backlight module of the LCDdevice and is an essential element related to the light utilizationefficiency. In addition to the light guidance and the control ofexiting-light, the light guide plate is designed to elevate luminanceand light uniformity, therefore improving the light utilizationefficiency and optimizing the visual quality. In addition, accompanyingthe technology improvement in the display device industry as well as theuser demands, display devices are getting smaller and lighter.According, the interior components/elements of the display devices arerequired to have the same or even better function under the limitedvolume or space.

As FIG. 1A shows, the sheetless backlight module 1′ has less cost ofproduction due to no optical films such as diffuser or prism films usedand therefore is lighter and smaller than the conventional backlightmodule. On the other hand, since the sheetless backlight module does notuse the diffuser film, light exiting thereof is more direct and thelight energy is more centralized. However, the sheetless backlightmodule 1′ has defects of hot spot and light ray which are concerned invisual quality. In addition, along with the more-direct light-exiting,the light energy does not disperse enough and the view angle of thebacklight module 1′ is too small as shown in FIG. 1B.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a backlight moduleand a light guide plate to solve the problems of hot spot, light ray,and small view angle.

It is another object of the present invention to provide a backlightmodule and a light guide plate to improve the light utilizationefficiency.

It is another object of the present invention to provide a light guideplate to decrease the cost of production of the backlight module and toreduce the thickness of the backlight module.

The present invention provides a backlight module and a light guideplate. The light guide plate includes a body and a plurality of thelight-scattering units. The body has a light-exiting face, a bottomlocated opposite to the light-exiting face, and a light-entering endconnected to the light-exiting face and the bottom. The body further hasa plurality of microstructures. The plurality of microstructures areformed on the bottom and recessed in the body to form a plurality ofmicrospaces. In addition, the distribution density of themicrostructures on the bottom gradually increases as the distance to thelight-entering end increases. The shape of the space formed due to eachof the plurality of microstructures includes a truncated cone shape, acone shape, a truncated pyramid shape, or a pyramid shape, wherein thespace has an opening on the bottom. The shape of the opening includescircle or polygon, wherein the diameter of the circular opening is lessthan 50 micrometer; the diameter of the circumscribed circle of thepolygonal opening is less than 50 micrometer. In addition, each spaceformed due to the microstructure shrinks in a direction away from theopening. As a result, an angle between the normal line of the side walland the normal line of the bottom is an acute angle less than 50degrees.

The pluralities of light-scattering units are disposed in the pluralityof spaces formed due to the plurality of microstructures recessed in thebody. The light-scattering unit is composed of at least a diffusivereflective material. The diffusive reflective material includes titaniumdioxide, silicon dioxide, resin, or a combination thereof. Thelight-scattering units are light-diffusive and a value of bidirectionscattering distribution function (BSDF) thereof is greater than a valueof BSDF of the body. The light-scattering units can be disposed in thespaces in the manner that the light-scattering unit respectivelycompletely fills the spaces or partially occupying the spaces. Thelight-scattering unit in the space intimately contacts the top portionof the space and the side wall around the top portion, i.e. the body ofthe light guide plate around the microstructures is covered by thediffusive reflective material, rather than being exposed to air.

The present invention further provides a manufacturing method of thelight guide plate, including steps: forming the plurality ofmicrostructures on the bottom of the body and recessed in the body;preparing a fluid solution containing at least a diffusive reflectivematerial; distributing the fluid solution on the bottom; driving thefluid solution to flow into the plurality of microstructures; removingthe fluid solution outside the microstructures; solidifying the fluidsolution to form the plurality of light-scattering units in theplurality of microstructures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a cross-sectional schematic view of the conventionalsheetless backlight module;

FIG. 1B is a simulation chart of view angle of the conventionalsheetless backlight module;

FIG. 2 is a cross-sectional schematic view of the embodiment of thelight guide plate of the present invention;

FIG. 3A is a cross-sectional schematic views of the embodiment of thebody of the light guide plate of the present invention;

FIGS. 3B-3C are bottom views of the embodiment of the body of the lightguide plate of the present invention;

FIGS. 4A-4B are cross-sectional schematic views of another embodiment ofthe body of the light guide plate of the present invention;

FIG. 4C is a bottom view of the embodiment of the body of the lightguide plate shown in FIG. 4B;

FIGS. 4D-4F are cross-sectional schematic views of another embodiment ofthe body of the light guide plate of the present invention;

FIGS. 5A-5C are cross-sectional schematic views of another embodiment ofthe light guide plate of the present invention;

FIG. 6 is a cross-sectional schematic view of another embodiment of thelight guide plate of the present invention;

FIG. 7 is a cross-sectional schematic view of another embodiment of thelight guide plate of the present invention;

FIG. 8 is a flow chart of a manufacturing method of the light guideplate of the present invention;

FIG. 9A is a schematic view of the embodiment of the sheetless backlightmodule of the present invention;

FIG. 9B is a simulation chart of view angle of the embodiment of thesheetless backlight module shown in FIG. 9A; and

FIG. 10 is a schematic view of another embodiment of the sheetlessbacklight module of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As the embodiment shown in FIG. 2, the light guide plate 10 of thepresent invention for a sheetless backlight module includes a body 100and a plurality of light-scattering units 300. The body 100 includes alight-exiting face 110, a bottom 120 located opposite to thelight-exiting face 110, and a light-entering end 130 located on one sideof the light-exiting face 110 and the bottom 120 and connected to thelight-exiting face 110 and the bottom 120. When the light guide plate 10is used in the backlight module (described later), the light emitted bythe light source enters the body 100 through the light-entering end 130.The light preferably leaves the light guide plate 10 from thelight-exiting face 110 and then enters such as a display panel. Thelight-entering end 130 can be located on one side or two opposite sidesof the body 100. The plurality of light-scattering units 300 arecomposed of material(s) different from material(s) of the body 100 andhave optical characteristics different from optical characteristics ofthe body 100. The light-scattering units 300 are preferably formed onthe bottom 120 of the body 100.

The body 100 further has a plurality of microstructures 200, as shown inFIG. 3A. The plurality of microstructures are formed on the bottom 120and recessed in the body 100 to form a plurality of microspaces 2000.The plurality of microstructures 200 are distributed evenly or unevenlyon the bottom 120, as shown in FIGS. 3B and 3C, respectively. On theother hand, the microstructures may be distributed regularly orirregularly. Preferably, the density of the microstructures 200distributed on the bottom 120 gradually increases as the distance to thelight-entering end 130 increases. As a result, the light exit rate fromthe light-exiting face 110 closer to the light-entering end 130 issmaller than the light exit rate from the light-exiting face 110 awayfrom the light-entering end 130. Accordingly, the light entering thebody 100 from the light-entering end 130 can have a longer retentiontime and a larger propagation range in the body 100. All in all, thedistribution of microstructures 200 shown in FIG. 3C can elevateuniformity of the light exiting from the light-exiting face 110 of thelight guide plate 10.

Each of the plurality of microspaces 2000 formed due to the plurality ofmicrostructures has an opening 210 a, as shown in FIG. 3A, wherein aperspective view of the microspace 2000 is further shown on the bottomright in FIG. 3A. In addition to the truncated cone shape shown in FIG.3A, the shape of the space 2000 can include other suitable shapes, suchas a cone, a truncated pyramid, or a pyramid as shown in FIGS. 4A, 4B,or 4D. For example, the pyramid may be a triangular pyramid, a tetrapyramid, etc. Each space 2000 shrinks in a direction away from theopening 210 a or 210 b. As a result, when the space 2000 having atruncated cone shape or a truncated pyramid shape has a top portion 230opposite to the opening 210 a or 210 b, the area of the top portion 230is smaller than that of the opening 210; in other words, the projectionof the top portion 230 on a plane where the opening 210 lies is withinthe range of the opening 210.

As shown in FIG. 3B, FIG. 3C, and FIG. 4C, which is a bottom view of theembodiment shown in FIG. 4B, the shape of the opening of the space 200includes a circle or a polygon. In the embodiment that the space 2000has the cone shape or the truncated cone shape, the shape of the opening210 a is a circle having a diameter D less than 50 micrometer. On theother hand, in the embodiment that the space 2000 has the pyramid shapeor the truncated pyramid shape, the shape of the opening 210 b is apolygon, wherein the diameter of the circumscribed circle of thepolygonal opening 210 b is preferably less than 50 micrometer. Forexample, as the space 2000 is a tetra pyramid with a quadrangularopening 210 b, the diameter of the circumscribed circle of thequadrangular opening 210 b is preferably less than 50 micrometer.

Furthermore, each of the microstructures 200 has a side wall 220enclosing the space 2000. Since the space 2000 formed due to themicrostructure 200 includes the cone shape, the pyramid shape, thetruncated cone shape, or the truncated pyramid shape, the space 2000 hasa narrow top and a wide bottom so that the side wall 220 inclines to thespace 2000. In other words, as shown in FIGS. 3A, 4A, 4B, and 4D, anangle between the normal line n1 of the side wall 220 and the normalline n2 of the bottom 120 is an acute angle A, wherein the acute angle Ais preferably less than 50 degrees. If the conditions that the diameterof the opening or the diameter of the circumscribed circle of theopening is less than 50 micrometer and that the acute angle A is lessthan 50 degrees are fulfilled, the space 2000 formed due to themicrostructure 200 is not limited to the above-mentioned shapes. Forexample, as FIGS. 4E-4F show, the space 2000 may be a cone having arectangular top cave, a cone having a cone-shaped top cave, or any otherpossible shapes.

As FIGS. 2 and 5A-5C show, the plurality of light-scattering units 300of the body 100 are disposed respectively in the plurality of spaces2000 formed due to the plurality of microstructures 200 recessed in thebody 100. The light-scattering unit 300 is composed of at least onediffusive reflective material so as to have optical characteristicsdifferent from the body 100. The diffusive reflective materialpreferably includes titanium dioxide, silicon dioxide, resin, or acombination thereof, wherein the density of the material(s) can beadjusted in accordance with factors such as the thickness of the lightguide plate or the height of the microstructure. The light-scatteringunits 300 are light-diffusive and a value of bidirection scatteringdistribution function (i.e. a BSDF value) thereof is greater than avalue of bidirection scattering distribution function of the body 100.Generally speaking, the light-scattering property (i.e., BSDF) isdetermined by emitting a light beam with a specific angle of incidenceto a sample (e.g., the scattering-unit 300 of the present invention),and then scanning the space corresponding to the scattering by a sensorto acquire energy of the light scattering in various angles to thespace. In addition, the light-scattering property of thelight-scattering units 300 is specifically the property of reflectivescattering, i.e., after reaching the light-scattering unit 300, thelight mostly reflects and scatters, rather than penetrating thelight-scattering unit 300 and then scattering.

The light-scattering units 300 can be selectively disposed in the spaces2000 formed due to the microstructures 200; however, in the preferredembodiment of the present invention, all spaces 2000 formed due to theplurality of microstructures 200 have the light-scattering units 300disposed therein, respectively. As a result, when the pluralities ofmicrostructures 200 are distributed on the bottom 120 evenly, thelight-scattering units 300 are also distributed on the bottom 120evenly. If the pluralities of microstructures 200 are distributed on thebottom 120 unevenly, the light-scattering units 300 are also distributedon the bottom 120 unevenly. In addition, no matter how thelight-scattering units 300 are distributed on the bottom 120, thedensity of the diffusive reflective material(s) in the light-scatteringunit 300 may differ in accordance with the location of thelight-scattering unit 300 on the bottom 120. For example, in accordancewith different requirement for light exiting from the light-exiting face110 of the light guide plate 10, the density of the diffusive reflectivematerial(s) in the light-scattering unit 300 gradually decreases orincreases as the distance from the light-scattering unit 300 to thelight-entering end 130 increases.

The light-scattering units 300 are preferably disposed in the spaces2000 in a way substantially completely filling the spaces 2000. As FIG.2 shows, if the light-scattering unit 300 substantially completely fillsthe truncated cone-shaped space 2000, the light-scattering unit 300 willhave the same truncated cone shape. Similarly, as shown in FIG. 5A, 5B,or 5C, the light-scattering unit 300 will have the cone shape, thetruncated pyramid shape, or the pyramid shape. In other embodiments,however, it is not necessary that the light-scattering unit 300 fillsthe space 2000 completely; that is, the light-scattering units 300 canstill have a light-reflective scattering function even not completelyfilling the spaces 2000. As such, the production cost and themanufacture process can be reduced. As the light guide plate 10 b shownin FIG. 6, the light scattering unit 300 occupies the space 2000 mostlybut not entirely, wherein the light-scattering unit 300 still intimatelycontacts the top portion 230 of the space 2000 and the side wall 220around the top portion 230. In other words, the body 100 of the lightguide plate 10 around the microstructures 200 is covered by thediffusive reflective material(s) rather than being exposed to air.Furthermore, in another embodiment as shown in FIG. 7, with regard tothe light guide plate 10 c, the light-scattering unit 300 can bedisposed with a shape conformal to the outline of the space 2000; thatis, the light-scattering unit 300 is conformally applied to the surfaceof the top 230 and the side wall 220. Similarly, the body 100 of thelight guide plate 10 c shown in FIG. 7A around the microstructures 200is also covered by the diffusive reflective material(s).

The present invention further includes a manufacturing method of thelight guide plate. As shown in FIG. 8, in one embodiment, themanufacturing method of the light guide plate includes step 801: forminga plurality of microstructures on the bottom of the body of the lightguide plate, wherein the microstructures are recessed in the body fromthe bottom. For example, in the step 801, when the light guide plate isformed by cutting or injection molding, the microstructures recessed inthe body from the bottom can be formed by any suitable process such asetching, electroforming, cutting, or imprinting. In other embodiments,however, the microstructures can be integrally formed simultaneously asthe light guide plate is formed. The method further includes step 802:preparing a fluid solution containing at least a diffusive reflectivematerial. In the step 802, it is preferred to choose a photo-curingfluid as the solvent of the solution while titanium dioxide, silicondioxide, resin, or the combination thereof is used as the solute to beadded to the solvent, wherein the solute and the solvent are well mixedto form a homogeneous mixture as the fluid solution. The solute ispreferred in a form of powder or microparticle; however the solute canbe liquid. The step 802 further includes determining the density of thediffusive reflective material(s) in the light-scattering unit to serveas the basis for the total amount of the solute to be added into theunit volume of the solvent during the preparation of the fluid solution.The step 802 may also include preparing the fluid solutions havingdifferent density of the diffusive reflective material(s). The methodfurther includes step 803: distributing the fluid solution on thebottom, wherein the bottom may include the plurality of microstructuresformed on the bottom and the plurality of spaces formed due to thesemicrostructures recessed in the body. Specifically, the step 803includes disposing the light guide plate so that the bottom thereoffaces upward, i.e. the openings of the spaces formed due to themicrostructures face upward, and then distributing the fluid solution onthe bottom, so that the fluid solution flows into the spaces from theopenings. In addition, the step 803 may include distributing the fluidsolutions having different density of the diffusive reflectivematerial(s) on different portions of the bottom.

In practice, the fluid solution can be controlled to enter the spacesdirectly. For example, the step 803 can print the bottom with the fluidsolution by screen printing. Since the screen printing includesproviding a stencil, disposing the stencil on the bottom of the body ina manner that the meshes of the stencil are aligned to the openings ofthe spaces, and printing. As a result, the steps 803 of screen printingsubstantially distribute the fluid solution into the spaces formed dueto the microstructures directly. After step 803, the method furtherincludes step 804: driving the fluid solution to flow into the pluralityof the microstructures. In the preferred embodiment of the presentinvention, it is preferred to make sure that every space formed due tothe microstructure has the fluid solution flowing therein and to ensurethat a predetermined amount of the fluid solution is present in thespace. In another aspect, in practice, the step 804 can be performedparticularly by moving the light guide plate in a speed, such ashorizontally shaking the light guide plate on a shaker, in order toincrease the flowing speed and the uniformity as the fluid solutionflows into the spaces.

Furthermore, taking the manufacturing method of the light guide plateshown in FIG. 2 and FIGS. 5A-5C for example, the step 804 includesdriving the fluid solution to substantially completely fill the spacesformed due to the plurality of the microstructures. In anotherembodiment of the manufacturing method, such as the manufacturing methodof the light guide plate 10 a shown in FIG. 6, the step 804 preferablyincludes enabling each of the spaces to have equal amount of the fluidsolution. In a further embodiment, such as the manufacturing method ofthe light guide plate 10 c shown in FIG. 7, the step 804 includesenabling the fluid solution to cover the surface of the wall includingthe side wall and the top portion around the spaces. In sum, the step804 is performed to ensure that the body of the light guide plate aroundthe microstructures is generally covered by the diffusive reflectivematerial(s), rather than being exposed to air.

The method further includes step 805: removing the fluid solutionoutside the microstructures, i.e. scraping the fluid solution that isformed outside the microstructures during the steps 803-804 from thebottom by such as a scraper to ensure that the fluid solution remainsonly in the spaces formed due to the microstructures. On the other hand,if the step 803 involves distributing the fluid solution on the bottomby screen printing, the time required for performing the step 805 willbe reduced. In addition, the step 805 will be omitted in themanufacturing method of the light guide plate shown in FIG. 6 or FIG. 7.In step 806: solidifying the fluid solution to form the plurality oflight-scattering units in the plurality of microspaces formed due to theplurality of microstructures recessed in the body further includes lightcuring the fluid solution. The solidified fluid solution contactstightly the wall around the spaces to form the plurality oflight-scattering units of the light guide plate.

The present invention also includes a sheetless backlight module havingthe above-mentioned light guide plate or a light guide platemanufactured by means of the above-mentioned method. As the embodimentshown in FIG. 9A, a backlight module 1 includes the light guide plate 10as shown in FIG. 2, a light source 50, and a reflective plate 60. Thelight source 50 is disposed at the side of the body 100 of the lightguide plate 10 having the light-entering end 130, wherein alight-emitting area 54 of the light source 50 faces the light-enteringend 130. The reflective plate 60 is disposed at a side of the lightguide plate 10 and faces the bottom 120 of the light guide plate 10. Thelight emitted from the light-emitting area 54 enters the body 100 of thelight guide plate 10 from the light-entering end 130 and advances in adirection away from the light-entering end 130 by total reflection inthe body 100. In addition, the propagation of the light in the body 100includes advancing toward the plurality of the microstructures 200.Since the body 100 of the light guide plate 10 around themicrostructures 200 is covered by the diffusive reflective material(s),the light advancing toward the microstructures will arrive at thelight-scattering units 300 and is then reflected and scattered away fromthe microstructures 200 to the light path P as shown in FIG. 9A. Inother words, the light-scattering units 300 containing the diffusivereflective material(s) increases the light distribution at angles otherthan the angle of reflection and therefore increases the light emittingangle and solves the problems of hot spot and light ray. Furthermore, inthe embodiment shown in FIG. 9A, the reflective plate 60 is composed ofreflection material; in other words, a value of bidirection scatteringdistribution function of the reflective plate 60 is less than the valueof bidirection scattering distribution function of the light-scatteringunits 300. The retro-reflection feature of the reflective plate 60allows the reflective plate 60 to reflect the light that leaves thelight guide plate undiffusively, so that the light can enter the lightguide plate again. As a result, the light energy is well utilized andthe loss of light energy is reduced.

FIG. 9B is a simulation chart of view angle of the embodiment of thesheetless backlight module shown in FIG. 9A. The abscissa axisrepresents the view angle ranging from −90 to 90 degrees while theordinate axis represents a luminance (%) of the light exiting from thelight-exiting face 110. Therefore, from FIG. 9B, a percentage ofluminance of the light at a certain view angle on the basis of thedetectable maximum luminance can be obtained, wherein the view angle isthe angle between a viewer and the normal line N of the light-exitingface 110. For example, when the viewer looks at the light-exiting face110 squarely, the view direction of the viewer is on the normal line N,wherein the view angle is zero degree. Further speaking, if thedetectable view angle is wider, a wider range of light-exiting angle canbe obtained. If the detectable view angle is narrower, a narrower rangeof light-exiting angle can be obtained, wherein the light energy is morecentralized since the light is focus in a smaller range ofexiting-angle.

The simulation charts of the embodiment of the backlight module of thepresent invention and the conventional backlight module shown in FIG. 9Band FIG. 1B are compared. The angle range θB having 50% of thedetectable luminance of the light in FIG. 9B is greater than the anglerange having 50% of the detectable luminance of the light θA in FIG. 1B.In other words, the sheetless back light module 1 shown in FIG. 9A,which has the light guide plate 10 of the present invention, has a widerrange of light-exiting angle to solve the problem of small view angle.

In another aspect, since the light-scattering units 300 distributed onthe bottom 120 of the light guide plate 10 prevent the light thatarrives at the microstructures 200 with an incident angle smaller thanthe critical angle from leaving the body 100 and entering the airmedium, the loss of light can be reduced and the light utilizationefficiency is increased. Accordingly, in other embodiments, thebacklight module 1 may not have a reflective plate, as shown in FIG. 10.

Although the preferred embodiments of present invention have beendescribed herein, the above description is merely illustrative. Thepreferred embodiments disclosed will not limited the scope of thepresent invention. Further modification of the invention hereindisclosed will occur to those skilled in the respective arts and allsuch modifications are deemed to be within the scope of the invention asdefined by the appended claims.

What is claimed is:
 1. A manufacturing method of a light guide plate, comprising: forming a plurality of microstructures on a bottom of a body of the light guide plate, wherein the microstructures are recessed in the body from the bottom; preparing a fluid solution containing at least a diffusive reflective material; distributing the fluid solution on the bottom; driving the fluid solution to flow into the plurality of microstructures; removing the fluid solution outside the microstructures; and solidifying the fluid solution to form a plurality of light-scattering units in the plurality of microstructures.
 2. The manufacturing method of the light guide plate of claim 1, wherein the step of distributing the fluid solution on the bottom further includes distributing the fluid solution by screen printing.
 3. The manufacturing method of the light guide plate of claim 1, wherein the step of driving the fluid solution to flow into the plurality of microstructures further includes driving the fluid solution to fill the microstructures.
 4. The manufacturing method of the light guide plate of claims 1, wherein the step of removing the fluid solution outside the microstructures further includes scraping the fluid solution from the surface of the bottom.
 5. The manufacturing method of the light guide plate of claim 1, wherein the step of solidifying the fluid solution further includes light curing the fluid solution. 